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(11) | EP 2 810 517 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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Efficient multiplexing of ePDCCH signals Effizientes Multiplexen für ePDCCH-Signale Multiplexage efficace des signaux de type ePDCCH |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention relates to a method and system for physical downlink control channel multiplexing and the associated blind decoding. Specifically, the invention relates to resource multiplexing between physical downlink control channel and the data channels.
[0002] LG-Ericsson: "Consideration on enhanced PDCCH to REs mapping"; R1-114189, 3GPP TSG RAN WG1 # 67, 14th-18th November, 2011 discloses an investigation of the mapping of enhanced PDCCH to REs.
[0003] Modern wireless communications standards and systems rely on intricate scheduling schemes to efficiently utilize the limited radio resources and maximize the system throughput. 4G cellular standards feature orthogonal frequency division multiple access (OFDMA) where resource scheduling is needed for both downlink and uplink transmission. The scheduling is done at the base station in a centralized fashion, and the scheduling grants can be for downlink transmission or uplink transmission. Both downlink and uplink grants are transmitted in Physical Downlink Control CHannel (PDCCH). The adjective "physical" before "downlink control channel" emphasizes that such control signaling occurs very frequently, i.e., every 1 ms, so that it can dynamically adapt to the fast fading of the channel. Frequent signaling, although crucial for dynamic link adaptation, is very expensive, in the sense that its overhead is high, in particular for those mobile terminals at cell edges. Hence, there should be a limit for the overhead of physical downlink control channel, so that there are enough physical resources for downlink data transmissions.
[0004] In 3GPP LTE, physical downlink control channel (PDCCH) is time multiplexed with Physical Downlink Shared Channel (PDSCH) which carries the downlink data. More specifically, the physical control channel occupies the entire first few OFDM symbols, spanning over the whole system bandwidth. Downlink and uplink grants of different users are encoded, modulated, cross-interleaved and mapped to those OFDM symbols, designated for PDCCH. The design principles of PDCCH are: 1) to concentrate PDCCH in the first few OFDM symbols to allow earlier decoding of DL/UL grants; 2) to ensure robust decoding of PDCCH. The purpose of the cross-interleaving and the spreading over entire system bandwidth is to randomize the frequency-selective fading and interference, and to achieve robustness.
[0005] In LTE-A relay, a new physical control channel is introduced to the relay backhaul link, called relay physical downlink control channel (R-PDCCH) [1]. R-PDCCH takes some resources in the downlink data channel (PDSCH) region. R-PDCCH can occupy an entire physical resource block (PRB) pair consisting of two slots, or just one slot of PRB. When both slots are occupied by R-PDCCH, the multiplexing between R-PDCCH and PDSCH is called frequency division multiplexing (FDM). When only one slot (especially the first slot) is occupied by R-PDCCH, the multiplexing between R-PDCCH and PDSCH is called time division multiplexing (TDM) + frequency division multiplexing (FDM). To reduce the decoding latency, DL grants for relay backhaul link can only be transmitted in the first slot(s) of PRB pair(s), whereas UL grants for relay backhaul can only be transmitted in the second slot(s) of PRB pair(s). R-PDCCH can be cross-interleaved or non cross-interleaved over different relay nodes. For cross-interleaved R-PDCCH, only common reference signal (CRS) can be used for demodulation. The cross-interleaved R-PDCCH bears a lot resemblance to PDCCH where the decoding robustness is a top consideration. Due to CRS demodulation, cross-interleaved R-PDCCH cannot benefit from beamforming, similar to PDCCH. Cross-interleaving also prevents the frequency selective scheduling gain. In contrast, the design principle of non cross-interleaved R-PDCCH is to exploit beamforming and frequency selective gain where demodulation reference signal (DMRS) is preferred. DMRS is present only in physical resource blocks that contain R-PDCCH or PDSCH, and goes through the same precoding as R-PDCCH or PDSCH. Therefore, precoding is totally transparent to R-PDCCH, i.e., no need for separate signaling to indicate precoding matrices used at the transmitter.
[0006] Traditional cellular networks consist primarily of macro base stations whose transmit power and antenna gains are the same. The site-to-site distance is almost constant and the network grids are quite uniform. The fast growing demand for system capacity motivates the deployment of a large number of low power nodes such as remote radio head (RRH) pico, femto nodes, to offload the traffic from the macro and increase the throughput in hot-spots. The mixture of macro, remote radio head, pico and femto cells constitutes the so called heterogeneous networks (HetNets). Interference scenarios become more complex in HetNets, not only for data channels such as PDSCH, but also for control channels such as PDCCH. There are several interference coordination schemes for PDSCH in HetNets deployment, one of them being partial frequency reuse where orthogonal resources are allocated for users near cell edges. However, such scheme cannot be used for PDCCH since it occupies the entire system bandwidth. In another HetNet scenario, remote radio head (RRH) is with the same cell ID as of macro cell, thus appearing transparent to users. Transparent RRH can significantly improve the system throughput by dynamic joint transmission over macro antennas and RRH. But, it has issue with limited resources for PDCCH which is shared by all scheduled users within the coverage area, i.e., there is no cell splitting gain of PDCCH. So there is a strong motivation of improving the capacity of PDCCH and mitigating the strong interference in HetNets. The enhanced physical downlink control channel is called ePDCCH.
[0007] According to the present invention there are provided a method of, and a system for, multiplexing enhanced physical downlink control channels as defined in the independent claims. Preferred embodiments are provided in the dependent claims.
[0008] The present invention is defined and limited only by the scope of the appended claims. In the following, any embodiment(s) referred to and not falling within the scope of said appended claims is (are) to be interpreted as example(s) useful for understanding the present invention.
[0009] In an embodiment, the method is a method according to independent claim 1 and further detailed in dependent claims 2-7.
[0010] The system is a system according to independent claim 8 and further detailed in dependent claims 9-14.
[0011] Figure 1 shows an example of resource multiplexing of enhanced physical downlink control channel and downlink data channel.
[0012] The invention considers four key design principles for enhanced physical downlink control channels: 1) to facilitate frequency domain interference coordination; 2) to exploit beamforming/precoding gain and frequency selectivity gain; 3) to reduce the decoding latency; 4) to ensure certain robustness of control channel decoding. Frequency domain interference coordination can be achieved by FDM multiplexing between downlink control channel and downlink data channel, for example, putting UL grants into the entire resource blocks, first and second slots. Different cells can configure different physical resource blocks for UL grants to avoid interference. Beamforming/precoding gain and frequency selectivity gain can be obtained by allowing TDM+FDM multiplexing between downlink control channel and downlink data channel, for example, putting DL/UL grant in the same resource blocks as for downlink data transmission, with the same precoding. Decoding latency can be kept small by restricting DL grants only in the first slot of physical resource blocks. Certain robustness of UL grant decoding can be accomplished by frequency distributed allocation of physical resource blocks and cross-interleaving of UL grants of different users. Cross-interleaving of UL grants also increases the packing efficiency, which helps to improve the control channel capacity.
[0013] The invention is illustrated in an example shown in Figure 1. There are five users, User 1 to 5, scheduled in this subframe. Each subframe contains two slots. We focus on the resource region not belonging to the legacy PDCCH (dark gray area). The light gray area is used for enhanced physical downlink control channel (ePDCCH) transmission. User 1 has only DL grant. User 2 has both DL grant and UL grant. User 3, User 4 and User 5 have only UL grants. DL grant of User 1 is transmitted in the first slot of a resource block where the second slot is used for User 1's downlink data transmission. User 1 also uses the adjacent resource block (in both the first and the second slots) for its downlink data transmission. DL grant and UL grant of User 2 are mixed and transmitted in the first slot of two resource blocks. User 2's downlink data is transmitted in the second slot of those two resource blocks. DL/UL grants of User 1 and User 2 can enjoy beamforming/precoding gain and frequency selectivity gain, the same way as their downlink data channels. UL grants of User 3, User 4 and User 5 are cross-interleaved, and mapped to both the first and the second slots of the two resource blocks. Those two resource blocks are frequency distributed to provide frequency diversity for decoding robustness.
[0014] In Figure 1, the number of physical resource blocks for DL/UL grants in the first slot is three in Figure 1. The number of physical resource blocks for UL grants in both the first slot and the second slot is two. Their numbers and locations are configured by higher layers.
[0015] User 1 to 5 first try to blindly decode DL/UL grants in the first slot of the three resource blocks. Assuming that DL/UL grant decoding has no errors, User 1 detects its DL grant which indicates that its downlink data is to be transmitted in those two adjacent resource blocks. Since User 1 knows that its DL grant occupies one of the physical resource blocks, it would proceed to decode the downlink data in the rest of total 3 slots in those two resource blocks. Upon the detection of its DL and UL grant, User 2 proceeds to decode the downlink data in the rest of total 2 slots in the two adjacent resource blocks. After the decoding in the first slot, User 3, User 4 and User 5 do not detect their DL/UL grants. Then they try to blindly decode the cross-interleaved UL grants in both slots of the two resource blocks. Upon the detection of those UL grants, User 3, User 4 and User 5 should prepare for UL data transmission in the next few subframes. The present invention is defined and limited only by the scope of the appended claims.
References
mapping scheduling grants of at least three users to physical resource blocks based on which types of scheduling grants each user has in a subframe,
wherein in case that a first user of the at least three users has only a scheduling grant for downlink data transmission, DL grant, in the subframe, the DL grant of the first user is mapped to a physical resource block in a first slot of the subframe where a second slot of the subframe is used for the first user's downlink data transmission,
wherein in case that a second user of the at least three users has both a DL grant and a scheduling grant for uplink data transmission, UL grant, in the subframe, the DL and UL grants of the second user are mixed and mapped to physical resource blocks in the first slot of the subframe where the second slot is used for the second user's downlink data transmission,
wherein in case that the third user of the at least three users has only UL grants in the subframe, the UL grants of the third user is cross-interleaved and mapped to the first and second slots where no enhanced physical downlink data channel is transmitted for the third user; and
multiplexing the enhanced physical downlink control channels containing the scheduling grants of the at least three users, by using a frequency division multiplexing scheme or a combination of frequency division multiplexing and time division multiplexing scheme.
separately configuring the physical resource blocks for transmission of the cross-interleaved UL grants of the third user and for transmission of the mixture DL and UL grants of the second user wherein the configuration is via higher layer signaling.
means for mapping scheduling grants of at least three users to physical resource blocks based on which types of scheduling grants each user has in a subframe comprising a first slot and a second slot,
wherein in case that a first user of the at least three users has only a scheduling grant for downlink data transmission, DL grant, in the subframe, the DL grant of the first user is mapped to a physical resource block in the first slot of the subframe where the second slot of the subframe is used for the first user's downlink data transmission,
wherein in case that a second user of the at least three users has both a DL grant and a scheduling grant for uplink data transmission, UL grant, in the subframe, the DL and UL grants of the second user are mixed and mapped to physical resource blocks in the first slot of the subframe, where the second slot is used for the second user's downlink data transmission,
wherein in case that the third user of the at least three users has only UL grants in the subframe, the UL grants of the third user is cross-interleaved and mapped to the first and second slots where no enhanced physical downlink data channel is transmitted for the third user; and
means for multiplexing the enhanced physical downlink control channels containing the scheduling grants of the at least three users, by using a frequency division multiplexing scheme or a combination of frequency division multiplexing and time division multiplexing scheme.
means for separately configuring the physical resource blocks for transmission of the cross-interleaved UL grants of the third user and for transmission of the mixture DL and UL grants of the second user wherein the configuration is via higher layer signaling.
Zuordnen von Planungsgewährungen von mindestens drei Benutzern zu physischen Ressourcenblöcken basierend darauf, welche Arten von Planungsgewährungen jeder Benutzer in einem Unterrahmen hat,
wobei, in einem Fall, dass ein erster Benutzer der mindestens drei Benutzer nur eine Planungsgewährung für Downlink-Datenübertragung, DL-Gewährung, in dem Unterrahmen hat, die DL-Gewährung des ersten Benutzers einem physischen Ressourcenblock in einem ersten Schlitz des Unterrahmens zugeordnet ist, wo ein zweiter Schlitz des Unterrahmens für die Downlink-Datenübertragung des ersten Benutzers verwendet wird,
wobei, in einem Fall, dass ein zweiter Benutzer der mindestens drei Benutzer sowohl eine DL-Gewährung als auch eine Planungsgewährung für Uplink-Datenübertragung, UL-Gewährung, in dem Unterrahmen hat, die DL- und UL-Gewährungen des zweiten Benutzers gemischt werden und physischen Ressourcenblöcken in dem ersten Schlitz des Unterrahmens zugeordnet sind, wo der zweite Schlitz für die Downlink-Datenübertragung des zweiten Benutzers verwendet wird,
wobei, in einem Fall, dass der dritte Benutzer der mindestens drei Benutzer nur UL-Gewährungen in dem Unterrahmen hat, die DL-Gewährungen des dritten Benutzers kreuzverschachtelt und dem ersten und zweiten Schlitz zugeordnet ist, wo kein verstärkter physischer Downlink-Steuerkanal für den dritten Benutzer übertragen wird; und
Multiplexen der verstärkten physischen Downlink-Steuerkanäle, die die Planungsgewährungen der mindestens drei Benutzer enthalten, durch Verwenden eines Frequenzmultiplex-Schemas oder einer Kombination aus Frequenzmultiplex- und Zeitmultiplex-Schema.
separates Konfigurieren der physischen Ressourcenblöcke zur Übertragung der kreuzverschachtelten UL-Gewährungen des dritten Benutzers und zur Übertragung der vermischten DL- und UL-Gewährungen des zweiten Benutzers, wobei die Konfiguration über eine Signalisierung einer höheren Schicht ist.
Mittel zum Zuordnen von Planungsgewährungen von mindestens drei Benutzern zu physischen Ressourcenblöcken basierend darauf, welche Arten von Planungsgewährungen jeder Benutzer in einem Unterrahmen hat, der einen ersten und einen zweiten Schlitz umfasst,
wobei, in einem Fall, dass ein erster Benutzer der mindestens drei Benutzer nur eine Planungsgewährung für Downlink-Datenübertragung, DL-Gewährung, in dem Unterrahmen hat, die DL-Gewährung des ersten Benutzers einem physischen Ressourcenblock in dem ersten Schlitz des Unterrahmens zugeordnet ist, wo der zweite Schlitz des Unterrahmens für die Downlink-Datenübertragung des ersten Benutzers verwendet wird,
wobei, in einem Fall, dass ein zweiter Benutzer der mindestens drei Benutzer sowohl eine DL-Gewährung als auch eine Planungsgewährung für Uplink-Datenübertragung, UL-Gewährung, in dem Unterrahmen hat, die DL- und UL-Gewährungen des zweiten Benutzers gemischt werden und physischen Ressourcenblöcken in dem ersten Schlitz des Unterrahmens zugeordnet sind, wo der zweite Schlitz für die Downlink-Datenübertragung des zweiten Benutzers verwendet wird,
wobei, in einem Fall, dass der dritte Benutzer der mindestens drei Benutzer nur UL-Gewährungen in dem Unterrahmen hat, die DL-Gewährungen des dritten Benutzers kreuzverschachtelt und dem ersten und zweiten Schlitz zugeordnet ist, wo kein verstärkter physischer Downlink-Steuerkanal für den dritten Benutzer übertragen wird; und
Mittel zum Multiplexen der verstärkten physischen Downlink-Steuerkanäle, die die Planungsgewährungen der mindestens drei Benutzer enthalten, durch Verwenden eines Frequenzmultiplex-Schemas oder einer Kombination aus Frequenzmultiplex- und Zeitmultiplex-Schema.
Mittel zum separaten Konfigurieren der physischen Ressourcenblöcke zur Übertragung der kreuzverschachtelten UL-Gewährungen des dritten Benutzers und zur Übertragung der vermischten DL- und UL-Gewährungen des zweiten Benutzers, wobei die Konfiguration über eine Signalisierung einer höheren Schicht ist.
le mappage d'autorisations de planification d'au moins trois utilisateurs à des blocs de ressource physiques sur la base des types d'autorisations de planification dont dispose chaque utilisateur dans une sous-trame,
dans lequel, dans le cas où un premier utilisateur des au moins trois utilisateurs ne dispose que d'une autorisation de planification pour une transmission de données en liaison descendante, autorisation DL, dans la sous-trame, l'autorisation DL du premier utilisateur est mappée à un bloc de ressource physique dans un premier intervalle de la sous-trame où un deuxième intervalle de la sous-trame est utilisé pour la transmission de données en liaison descendante du premier utilisateur,
dans lequel, dans le cas où un deuxième utilisateur des au moins trois utilisateurs dispose à la fois d'une autorisation DL et d'une autorisation de planification pour une transmission de données en liaison montante, autorisation UL, dans la sous-trame, les autorisations DL et UL du deuxième utilisateur sont mélangées et mappées à des blocs de ressource physiques dans le premier intervalle de la sous-trame où le deuxième intervalle est utilisé pour la transmission de données en liaison descendante du deuxième utilisateur,
dans lequel, dans le cas où le troisième utilisateur des au moins trois utilisateurs ne dispose que d'autorisations UL dans la sous-trame, les autorisations UL du troisième utilisateur sont entrelacées de manière croisée et mappées aux premier et deuxième intervalles où aucun canal de données en liaison descendante amélioré n'est transmis pour le troisième utilisateur ; et
le multiplexage des canaux de commande de liaison descendante améliorés contenant les autorisations de planification des au moins trois utilisateurs, à l'aide d'un plan de multiplexage par répartition en fréquence ou d'un plan de multiplexage par répartition en fréquence et de multiplexage par répartition dans le temps.
configuration séparée des blocs de ressource physiques pour une transmission d'autorisations UL entrelacées de manière croisée du troisième utilisateur et pour une transmission du mélange d'autorisations DL et UL du deuxième utilisateur, la configuration s'effectuant par le biais d'une signalisation de couches supérieures.
un moyen permettant le mappage d'autorisations de planification d'au moins trois utilisateurs à des blocs de ressource physiques sur la base des types d'autorisations de planification dont dispose chaque utilisateur dans une sous-trame comprenant un premier intervalle et un deuxième intervalle,
dans lequel, dans le cas où un premier utilisateur des au moins trois utilisateurs ne dispose que d'une autorisation de planification pour une transmission de données en liaison descendante, autorisation DL, dans la sous-trame, l'autorisation DL du premier utilisateur est mappée à un bloc de ressource physique dans un premier intervalle de la sous-trame où le deuxième intervalle de la sous-trame est utilisé pour la transmission de données en liaison descendante du premier utilisateur,
dans lequel, dans le cas où un deuxième utilisateur des au moins trois utilisateurs dispose à la fois d'une autorisation DL et d'une autorisation de planification pour une transmission de données en liaison montante, autorisation UL, dans la sous-trame, les autorisations DL et UL du deuxième utilisateur sont mélangées et mappées à des blocs de ressource physiques dans le premier intervalle de la sous-trame, où le deuxième intervalle est utilisé pour la transmission de données en liaison descendante du deuxième utilisateur,
dans lequel, dans le cas où le troisième utilisateur des au moins trois utilisateurs ne dispose que d'autorisations UL dans la sous-trame, les autorisations UL du troisième utilisateur sont entrelacées de manière croisée et mappées aux premier et deuxième intervalles où aucun canal de données en liaison descendante amélioré n'est transmis pour le troisième utilisateur ; et
un moyen permettant le multiplexage des canaux de commande de liaison descendante améliorés contenant les autorisations de planification des au moins trois utilisateurs, à l'aide d'un plan de multiplexage par répartition en fréquence ou d'un plan de multiplexage par répartition en fréquence et de multiplexage par répartition dans le temps.
un moyen permettant la configuration séparée des blocs de ressource physiques pour une transmission d'autorisations UL entrelacées de manière croisée du troisième utilisateur et pour une transmission du mélange d'autorisations DL et UL du deuxième utilisateur, la configuration s'effectuant par le biais d'une signalisation de couches supérieures.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Non-patent literature cited in the description
- LG-ERICSSONConsideration on enhanced PDCCH to REs mappingR1-114189, 3GPP TSG RAN WG1 # 67, 2011, [0002]
- Evolved Universal Terrestrial Radio Access (E-UTRA): Physical layer for relaying operation3GPP TS 36.216, [0016]